Um, the one I saw at erion racing was $8000!thebackdraft : I cannot remember where, I seen an online site with them. Not cheap. In fact so not cheap a cheap one will run like $800. You might be able to grab one for $600. They do have different grades of them, up to grade $1200 that I have seen and I'm sure there are more expensive ones.
To directly answer the question, It is a sprag clutch that connects the clutch to the shaft. It holds in one direction and free spins in the other. A very simplistic mechanism. The only thing about it that's special is it's astronomically ridiculous price.Heavy-Dee : I'm heard it talked about and I just don't know what it is. Sorry.